Age-hardenable, copper-base alloy



United States Pa AGE-HARDENABLE, COPPER-BASE ALLOY Norman W. Johnson, Oscar E. Harder, and Charles S.

Du Mont, Columbus, Ohio, assignors, by mesne assignments, to Wilbur B. Driver Company, Newark, N. 5., a corporation of New Jersey No Drawing. Application June 24, 1954, Serial No. 439,132

7 Claims. (Cl. 75-159) This invention relates to copper alloys and particularly to age-hardenable, copper-base alloys which have improved strength and ductility in the age-hardened condition.

It is well known that certain copper-base alloys can be strengthened and hardened by means of heat treatment commonly referred to as age hardening or precipitation hardening. The most common of these alloys are copper-beryllium, copper-titanium and copper-silicon alloys with additions of chromium, nickel, cobalt, iron, molybdenum, or manganese. These alloys may be solution annealed at high temperatures, usually between 1300 F. and 1900 F., and water quenched, which leaves them in a soft and ductile condition. While in this condition they can readily be cold worked. They then may be hardened and strengthened by annealing at a lower temperature, usually between 500 F. and 900 F. Higher hardness and strength may be obtained by cold working or cold reduction after solution annealing but before the age-hardening heat treatment.

Although these alloys have proved to be satisfactory in obtaining high hardness and strength, they have not been satisfactory in all of their resulting physical properties. This is particularly true in the case of ductility.

U. S. Patent 1,991,162, issued to Wilhelm Kroll, discloses copper-titanium alloys of theage-hardenable type. However, the physical properties revealed in this patent show an elongation value of only 6.5% when the tensile strength is about 142,000 p. s. i. There are also revealed in this patent additional hardening metals, such as nickel, chromium, manganese iron, cobalt, and molybdenum. However, it is stated (page 2, lines 293l) that the addition of one or more of these metals will reduce the elongation properties of the alloy.

The use of age-hardenable alloys is advantageous in that articles can be fabricated while in the fully annealed condition while the metal is soft, highly ductile, and easily cold worked and then, by a low-temperature heat treat- I :menhput in a hardened condition. It is frequently desirable to perform drawing or cold-work operations on the hardened metals and semi-finished articles; however, prior-art age-hardenable copper alloys exhibit very little ductility while in the age-hardened condition and cannot be successfully subjected to further cold working. It is also frequently desirable to retain a degree of ductility in the hardened article, such as in spring applications where the metal must be both hard and resilient.

It has now been discovered that certain age-hardenable copper alloys can be made which exhibit far superior ductility in the hardened condition than any known priorart age-hardenable copper alloys.

These alloys exhibit good electrical conductivity and are therefore particularly suited for use as spring elements in electrical apparatus where strength, ductility, and electrical conductivity are all important factors.

It is, therefore, an object of this invention to provide an age-hardenable, copper-base alloy which will exhibit sufficient ductility to be further fabricated after age hardening. Another object is to provide a copper-base alloy having high tensile strength, high hardness, and ductility. Another object of the invention is to provide an age-hardenable, copper-base alloy which will exhibit superior elongation values while in the cold-worked and age-hardened condition. Still another object is to provide an alloy suitable for applications in electrical apparatus which will exhibit superior spring qualities and good electrical conductivity. Other objects and advantageous features can best be understood from the following detailed description.

In general, this invention relates to a copper-base alloy which contains from 1 to 10% titanium and very small but effective amounts of cobalt, chromium, nickel, iron, molybdenum, and manganese. This alloy is capable of being age hardened. The alloy in its hardened condition exhibits unusual ductility when compared to the known copper-base alloys.

The improved copper-base alloy of this invention may contain from 1 to 10% titanium, .10 to 1.6% cobalt, .05 to .80% chromium, .04 to .62% nickel, .04 to .60% iron, .02 to 28% molybdenum and .005 to .08% manganese; however, for best results the preferred range may be said to be composed of from 2 to 6% titanium, .2 to .8% cobalt, .l to .4% chromium, .08 to 31% nickel, .075 to .3% iron, .035'to .14% molybdenum, .01 to .04% manganese, and the balance substantially copper.

A satisfactory method of adding the alloying elements in this invention is to add the titanium addition directly but to add the remaining alloying elements to the copper bath as one addition. For example, the alloy of this invention may be made by adding to a copper bath 1 to 10% titanium and A to 4% of an addition agent (or alloy) composed of about 40% cobalt, 20% chromium, 15.5% nickel, 15% iron, 7% molybdenum and 2% manganese. Residual or trace elements, including carbon, up to .72% may be present in the addition agent or alloy. The preferred range of alloying elements may be obtained by addition to molten copper of 2 to 6% titanium and .50 to 2% Man addition agent or alloy, such as described above.

It is to be understood that the use of an addition agent is merely a method of adding the alloying elements and that the percentages given for the above-mentioned addition agent may vary considerably so long as the resulting alloying elements fall within the ranges claimed.

The conventional heat treatments used to obtain age hardening in copper alloys may be satisfactorily employed to harden the alloy of this invention. It is preferred to solution anneal at 1600 F. or 1700 F. for about one hour and then water quench; however, temperatures of from 1300 F. to 1900 F. and a time at temperature of from /2 to 2 hours may be employed satisfactorily, Age hardening is preferably done at about'900 ;F.'for /2 to 6 hours, but may be accomplished at temperatures of from 500 F. to 1000 F. It will be obvious that the time required will depend on the temperature used, and that longer periods of time may be required for lower age-hardening temperatures. The degree of hardness and resulting ultimate tensile strength will depend to a great extent on the time the samples are held at these temperatures. This is particularly true of the hardening temperature and time. Generally the longer the alloy is held at this temperature the harder the resulting metal will be. To obtaineven higher hardness and tensile strength the alloy may be cold worked after the solution anneal or first heat treatment and before the age hardening heat treatment. Regardless of what hardness or tensile strength is reached the copper-base alloy of this invention will exhibit superior elongation to prior art 3 copper alloys showing the same hardness and ultimate tensile strength.

The following specific examples are given to more fully illustrate the properties of the copper-base alloy of this invention.

Example I A heat of the copper-base alloy was made which contained about 4.18% titanium and about 1 percent of an addition agent consisting of about 40% cobalt, 20% chromium, 15.5% nickel, 15% iron, 7% molybdenum, 2% manganese and less than .72% residual or trace elements.

Test specimens were solution heat treated at 1600 F. for one hour and water quenched. They were then age hardened at 900 F. for 6 hours. Tensile tests were pulled in which the yield strength was ascertained by using 0.2% offset, determined with the use of an extensometer and an autographic stress-strain recorder. The elongation was a measurement of percent in 2 inches.

The resulting average tensile test results of five test specimens was 137,500 p. s. i. ultimate tensile strength, 117,500 p. s. i. yield strength, and an elongation of 12.7%. The average hardness was about 28 Rockwell C.

The age-hardenable, copper-base alloys of this type appear to have a tendency to frequently neck down very sharply immediately before rupture. For this reason, reduction of area values were not included as it is believed they are not reliable measurements of ductility for these alloys.

Example ll Tensile tests were conducted on an alloy containing 4.18% titanium, and about 1% of an addition agent of the same composition as that used in Example I, and the balance substantially copper. These specimens were annealed at 1700 F. for one hour, water quenched, and cold rolled (40% reduction). They were then age hardened at 900 F. for one hour.

The resulting average tensile results of three test specimens was 153,000 p. s. i. ultimate tensile strength, 131,000 p. s. i. yield strength, and an elongation value of 10%. The average hardness was about 33 Rockwell C.

Example III Tensile tests were conducted on an alloy containing about 4% titanium, 1% addition agent of the same composition as that used in Example I, and the balance sub stantially copper. These specimens were annealed at 1600 F. for one hour, water quenched, and cold rolled (40% reduction).

Theaverage tensile results of three test specimens in the solution annealed and cold-rolled condition was 116,000 p. s. i. ultimate tensile strength, 107,000 p. s. i. yield strength, and an elongation value of 3%.

The average tensile results of three test specimens in the annealed, cold-rolled and age-hardened (900 F. for k hour) condition was 150,000 p. s. i. ultimate tensile strength, 136,000 p. s. i. yield strength, and an elongation value of 10%.

As a result of the above tests it can be seen that the age-hardenable or precipitatiomhardenable copper-base alloy of this invention is an improvement over the prior copper-titanium alloys, particularly since it possesses a better combination of strength and ductility when compared with the previously known copper-base alloys.

What is claimed is:

1. An age-hardenable, copper-base alloy consisting of 1 to 10% titanium, .10 to 1.6% cobalt, .05 to .80% chromium, .04 to .62% nickel, .04 to .60% iron, .02 to 28% molybdenum, .005 to 03% manganese, and the balance essentially copper, and characterized by superior ductility in the hardened condition when compared to other age-hardenable, copper-base alloys.

2. An age-hardenable, copper-base alloy consisting of l to 10% titanium, .10 to 1.6% cobalt, .05 to .80% chromium, .04 to .62% nickel, .04 to .60% iron, .02 to 28% molybdenum, .005 to 08% manganese, and the balance copper.

3. An age-hardenable, copper-base alloy consisting of 2 to 6% titanium, .2 to .8% cobalt, .1 to .4% chromium, .08 to 31% nickel, .075 to .3% iron, .035 to .14% molybdenum, .01 to .04% manganese, and the balance copper.

4. An age-hardenable, copper-base alloy consisting of 4% titanium, 40% cobalt, 20% chromium, .155% nickel, .15% iron, .07% molybdenum, 02% manganese, and the balance essentially copper, and characterized by superior ductility in the hardened condition when compared to other age-hardenable, copper-base alloys.

5. An age-hardenable, copper-base alloy consisting of 2 to 6% titanium; /2 to 2% of an addition alloy which consists essentially of 40% cobalt, 20% chromium, 15.5% nickel, 15% iron, 7% molybdenum and 2% manganese; the balance essentially copper, and characterized by superior ductility in the hardened condition when compared to other age'hardenable, copper-base alloys.

6. An age-hardenable, copper-base alloy consisting of 4% titanium; 1% of an addition alloy which consists essentially of 40% cobalt, 20% chromium, 15.5% nickel, 15% iron, 7% molybdenum and 2% manganese; the balance copper.

7. An age-hardenable, copper-base alloy consisting of 2 to 6% titanium, .2 to .8% cobalt, .1 to .4% chromium, .08 to 31% nickel, .075 to 3% iron, .035 to .14% molybdenum, .01 to .04% manganese, and the balance essentially copper, and characterized by superior ductility in the hardened condition when compared to other agehardenable, copper-base alloys.

References Cited in the tile of this patent UNITED STATES PATENTS 2,007,430 Maas July 9, 1935 2,031,315 Iennison Feb. 18, 1936 2,102,238 Filling et a1. Dec. 14, 1937 2,189,198 Comstock Feb. 6, 1940 2,430,419 Edens Nov. 4, 1947 

1. AN AGE-HARDENABLE, COPPER-BASE ALLOY CONSISTING OF 1 TO 10% TITANIUM, .10 TO 1.6% COBALT, .05 TO .80% CHROMIUM, .04 TO .62% NICKEL, .04 TO .60% IRON, .02 TO .28% MOLYBDENUM, .005 TO .08% MANGANESE, AND THE BALANCE ESSENTIALLY COPPER, AND CHARACTERIZED BY SUPERIOR DUCTILITY IN THE HARDENED CONDITION WHEN COMPARED TO OTHER AGE-HARDENABLE, COPPER-BASE ALLOYS. 